We have no plans to release the full Firefox browser for iOS. The iOS SDK agreement requires apps to use Apple's own JavaScript engine (or none at all, like Opera Mini which downloads pre-rendered pages from Opera's servers and cannot run JavaScript code in the client). Because of this, we have no supported way to distribute Firefox's rendering and JavaScript engine to iPhone users.
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You may be interested in this. https://itunes.apple.com/us/app/bookmarks-on-the-go/id550037184
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There is or was a browser prototype experiment called Junior. The key thing is this was not using the familiar Gecko layout engine due to Apple restrictions but rather uses the same WebKit rendering engine found in Safari for the iPad. And thanks to Apples restrictions on iOS application distribution, very few of the public may get to even get try this any time soon.

Mozilla only makes mobile Firefox for Android 2.2+.
https://wiki.mozilla.org/Mobile/Platforms#Other_Platforms
iPhone/iPad/iPod
''We have no plans to release the full Firefox browser for iOS. The iOS SDK agreement requires apps to use Apple's own JavaScript engine (or none at all, like Opera Mini which downloads pre-rendered pages from Opera's servers and cannot run JavaScript code in the client). Because of this, we have no supported way to distribute Firefox's rendering and JavaScript engine to iPhone users''.
.
You may be interested in this. https://itunes.apple.com/us/app/bookmarks-on-the-go/id550037184
.
.
There is or was a browser prototype experiment called Junior. The key thing is this was not using the familiar Gecko layout engine due to Apple restrictions but rather uses the same WebKit rendering engine found in Safari for the iPad. And thanks to Apples restrictions on iOS application distribution, very few of the public may get to even get try this any time soon.